Light emitting device

ABSTRACT

A light emitting device includes a plurality of oblong flexible substrates, each flexible substrate comprising a sheet-shaped base body and a wiring pattern formed on one face of the base body, and each flexible substrate having a plurality of light emitting sections disposed thereon; a plurality of a reflective layers, each reflective layer being disposed at a periphery of a respective light emitting section above a respective flexible substrate; an insulating reflective sheet made of a light reflecting resin, the reflective sheet having a plurality of through holes located such that the light emitting sections and at least a portion of the reflective layers are exposed via the through holes; and a plurality of adhesive members, each adhesive member adhering a respective flexible substrate to the reflective sheet in regions where the reflective layer is not formed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/901,765, filed Feb. 21, 2018, which is a continuation ofU.S. patent application Ser. No. 15/054,588, filed Feb. 26, 2016, nowU.S. Pat. No. 9,933,140, which claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2015-038645 filed Feb. 27, 2015, thecontents of which are incorporated herein by reference in theirentireties.

BACKGROUND

The present disclosure relates to a light emitting device that includesa flexible substrate.

A light emitting device employing a flexible substrate that includes areflective film covering a wiring pattern disposed on the sheet basematerial has been proposed. For example, Japanese Unexamined PatentApplication Publication No. 2014-131084 (Patent Document 1) discloses,as an example of the reflective film, an insulating white ink referredto as a white resist made of a silicone-based resin containing atitanium oxide.

Japanese Unexamined Patent Application Publication No. 2010-278016(Patent Document 2) discloses an electronic device constructed bysecuring an LED substrate to a metal sheet support using substrateholders, the LED substrate having a plurality of LEDs mounted on oneface and a reflective sheet made of a synthetic resin having throughholes at the positions corresponding to the LEDs.

SUMMARY

The light emitting device according to one embodiment comprises aplurality of oblong flexible substrates each including a wiring patterndisposed on one face of a sheet-shaped base body, light emittingsections disposed on the flexible substrates, a reflective layerdisposed at the peripheries of said light emitting sections directly onthe wiring pattern or spaced apart from said wiring patterns in thestacking direction on the flexible substrates, an insulating reflectivesheet made of a light reflecting resin including through holes so as toexpose the light emitting sections and at least one portion of thereflective layer, and an insulating adhesive member adhering theflexible substrates to the reflective sheet in the regions where saidreflective layer is not formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of the light emitting device accordingto Embodiment 1.

FIG. 2 is a schematic bottom view of the light emitting device accordingto Embodiment 1.

FIG. 3 is a schematic plan view of the light emitting device accordingto Embodiment 1 enlarging the region III indicated in FIG. 1.

FIG. 4 is a schematic cross-sectional view of the light emitting deviceaccording to Embodiment 1 viewed in the direction indicated by arrowsIV-IV in FIG. 3.

FIG. 5 is a schematic plan view of the flexible substrate of the lightemitting device according to Embodiment 1, illustrating one example ofthe wiring member formed under the reflective layer and an underlayer.

FIG. 6 is a schematic view of the flexible substrate of the lightemitting device according to a variation of Embodiment 1, illustratingone example of the wiring member formed under the reflective layer andthe underlayer.

FIG. 7A is a schematic view showing a production step for the lightemitting device according to Embodiment 1, which is a plan view of thereflective sheet.

FIG. 7B is a schematic view showing a production step for the lightemitting device according to Embodiment 1, which is a bottom view of thereflective sheet to which an adhesive member has been pasted.

FIG. 7C is a schematic view showing a production step for the lightemitting device according to Embodiment 1, which is a plan view of thereflective sheet which has undergone cutting and hole-making machiningoperations.

FIG. 7D is a schematic view showing a production step for the lightemitting device according to Embodiment 1, which is a bottom view of thereflective sheet to which flexible substrates have been adhered.

FIG. 8A is a schematic cross-sectional view of a lighting deviceincluding the light emitting device according to Embodiment 1.

FIG. 8B is a schematic cross-sectional view of a lighting deviceincluding the light emitting device according to Embodiment 2.

FIG. 8C is a schematic cross-sectional view of a lighting deviceincluding the light emitting device according to a variation ofEmbodiment 2.

FIG. 9 is a schematic bottom view of the light emitting device accordingto Embodiment 3.

FIG. 10 is a schematic bottom view of the light emitting deviceaccording to Embodiment 4.

FIG. 11A is a schematic plan view of the reflective sheet used in thelight emitting device according to Embodiment 5.

FIG. 11B is a schematic plan view of the light emitting device accordingto Embodiment 5.

FIG. 11C is a schematic exploded perspective view showing a stack of aplurality of light emitting devices according to Embodiment 5.

FIG. 12 is a schematic exploded perspective view of the light emittingdevice according to Embodiment 6 viewed from the side opposite theemission surface.

FIG. 13 is a schematic plan view of a flexible substrate of the lightemitting device according to a variation of Embodiment 6, showing anexample of the wiring pattern formed under the reflective layer and theunderlayer.

FIG. 14 is a schematic view showing a production step for the lightemitting device according to the variation of Embodiment 6, which is aplan view of a collective sheet for the flexible substrates beforeseparating.

FIG. 15 is a schematic view of the light emitting device according toEmbodiment 7, which is a plan view of the reflective sheet viewed fromthe rear face side.

FIG. 16 is a schematic view of the light emitting device according toEmbodiment 7, which is an enlarged cross section viewed in the directionindicated by arrows XVI-XVI in FIG. 15.

FIG. 17 is a schematic plan view of the light emitting device accordingto Embodiment 8.

DESCRIPTION

Embodiments of the invention will be described below with reference tothe drawings. The following embodiments, however, exemplify the lightemitting devices for the purpose of embodying the technical concepts ofthe invention, and do not limit the invention. The dimensions,materials, and shapes of the constituent elements, as well as therelative positioning thereof, described in the embodiments are offeredto merely as examples, and are not intended to limit the scope of theinvention to those described unless otherwise specifically noted. Thesizes of the components, their positional relationship, or the like,shown in the drawings might be exaggerated for clarity of explanations.

Embodiment 1

As shown in FIGS. 1 and 4, the light emitting device 1 according toEmbodiment 1 includes a plurality of oblong flexible substrates 10(hereinafter referred to as flexible substrates 10), reflective sheet20, and adhesive members 30. A plurality of light emitting sections 2and a reflective layer 8 are disposed at the peripheries of the lightemitting sections 2 on the flexible substrates 10. As shown in FIG. 1,the light emitting device 1 is provided with a plurality of flexiblesubstrates 10 (six shown here) disposed at a certain pitch P1 along thedirection perpendicular to the longitudinal direction of the flexiblesubstrates. Each flexible substrate 10 is provided with a plurality oflight emitting sections 2 (nine shown here) disposed at a certain pitchP2 along the longitudinal direction of the substrate. As shown FIG. 1,at one end of the upper faces 15 of the flexible substrates 10 (the leftend in FIG. 1), connectors 3 and 4 are mounted for electricallyconnecting an external power supply to a wiring pattern 13 shown FIG. 4via a wire harness, for example. The reflective sheet 20 has throughholes 21 so as to expose the light emitting sections 2 and at least oneportion of the reflective layers 8. The reflective sheet 20 also hasthrough holes 22 to expose the connectors 3 and 4. The upper faces 15 ofthe flexible substrates 10 are adhered to the rear face 26 of thereflective sheet 20 shown FIG. 2 via the adhesive members 30 shown FIG.4. The light reflecting surface (the face of the opposite to the rearface) of the reflective sheet 20 may be referred to as the front face 25hereinafter.

By disposing the insulating reflective film on the wiring pattern, thelight emitting device 1 can reduce electric shocks when the device ispowered, and protect against static electricity when the device ishandled, as well as improving the light reflectance of the substratesurface. The use of the white resist as a reflective film, however, maybe costly, and there may be a need for further cost reduction.

By including the reflective sheet, the light emitting device disclosedin Patent Document 2 can reflect the LED light. However, the LEDsubstrate and the reflective sheet are secured to the support usingsubstrate holders, which may make it difficult to produce a flexiblelight emitting device.

An object of certain embodiments of the present invention is to providea low-cost bendable light emitting device.

According to the light emitting devices of certain embodiments, abendable light emitting device can be produced at low cost by adheringflexible substrates to a reflective sheet.

Flexible Substrate

The flexible substrates 10 are disposed on the reflective sheet 20 withlight emitting elements 5 shown in FIG. 4 and other components mountedthereon. The pitch P1 between the flexible substrates 10 is set largerthan the width of a flexible substrate 10. The flexible substrates 10can be flexible printed boards having a wiring pattern on at least oneface of a sheet-shaped base body 11.

Each flexible substrate 10, as shown in FIG. 4, has a region where thebase body 11 and the wiring member 13 (wiring pattern) are stacked inthat order. On the wiring pattern 13, a region where an underlayer 7,which be used as a base for the reflective layer 8, alone is stacked,and a region where both the underlayer 7 and the reflective layer 8 arestacked. An adhesive layer 12 may be disposed between the base body 11and the wiring pattern 13. In the explanation below, the face of aflexible substrate 10 on which the wiring pattern 13 is formed may bereferred to as the upper face 15 (see FIG. 1), and the face on the basebody 11 side may be referred to as the back face 16 (see FIG. 2).

The base body 11 is the base of the flexible substrate 10, and is madeof a flexible insulating material. Polyimide, for example, is a suitablematerial for the base body 11. A molded reinforced plastic material madeby pre-impregnating a fibrous material, such as glass cloth or carbonfiber fabric, with a resin (e.g., glass fiber reinforced epoxycomposite, prepreg, or the like) is also suitable. A resin film, such aspolyethylene terephthalate (PET), polyethylene naphthalate,polyetherimide, polyphenylene sulfide, liquid crystal polymer, or thelike, may also be used. The thickness of the base body 11 is, forexample, in a range between about 10 and 300 μm. The base body 11 may beof either a single layer or multilayer structure.

The adhesive layer 12 adheres the base body 11 and the wiring pattern13. As material for the adhesive layer 12, examples include aurethane-based adhesive, or the like. The adhesive layer 12 may not berequired in the case where the base body 11 is made of a materialcapable of directly adhering to the wiring pattern 13 such as a moldedreinforced plastic material mentioned above, for example. In thesecases, the wiring member 13 is formed directly on the base body 11.

The wiring pattern 13 includes a conductive material. The wiring pattern13 is formed on the base body 11, for example, via an adhesive layer 12,which creates an electrical circuit when electrically connected to eachlight emitting element 5. The wiring member 13, for example, is made ofa copper foil. Besides that, an aluminum foil, aluminum alloy foil,stainless steel foil, or the like, can also be employed. The thicknessof the wiring pattern may be in a range between 10 μm and 50 μm.

As shown in FIGS. 3 and 4, a groove extending in the longitudinaldirection of the flexible substrate 10 is formed between two lines ofwiring member 13 a and 13 b which make up the wiring pattern 13 formedon the flexible substrate 10. The groove can be formed by removing thematerial forming the wiring pattern 13 formed on the flexible substrate10 by etching or the like.

As shown in FIG. 5, each of the two wiring members 13 a and 13 b isformed in a linear shape along a direction that is substantiallyparallel to the longitudinal direction of the flexible substrate 10. Thewidth of the flexible substrate 10 is denoted as W1, and the width ofeach of the two wiring members 13 a and 13 b is denoted as L1. The widthfrom an edge of each of the wiring members 13 a and 13 b to the outeredge of the base body 11 (hereinafter referred to as the creepagedistance) is denoted as L2, and the gap between the two wiring members13 a and 13 b is denoted as L3. In this case, preferably, therelationship expressed by the following formula (1) is established.

W1=2×L1+2×L2+L3  formula (1)

The widths L1 to L3 can suitably be selected in accordance with thepurpose and application. For example, in the case where the lightemitting device will be installed in a backlight for a television, thewidths L1, L2, and L3 can be set, for example, to 6 mm, 2 mm, and 200μm, respectively.

As shown in FIGS. 3 and 4, each light emitting element 5 is disposed onthe gap (groove) between the two wiring members 13 a and 13 b. Twoadjacent light emitting elements 5 are disposed so that electrodes ofthe light emitting elements having the same polarity adjacent each otherin the longitudinal direction of the flexible substrate 10 and areconnected in parallel.

Light Emitting Section 2

As shown in FIGS. 3 and 4, the light emitting element 5 is electricallyconnected to the wiring member 13. As shown in FIG. 1, the pitch P2 forarranging the light emitting sections 2 on the flexible substrates 10may be set larger than the width of a flexible substrate 10. The pitchP2 may be different from, or the same as, the pitch P1 described above.Here, as one example, the pitch P2 is the same as the pitch P1. Thelight emitting section 2 s, as shown in FIGS. 3 and 4, can include thelight emitting element 5 and a sealing member 6 respectively.

Light Emitting Element

The light emitting elements 5 emit light when a prescribed voltage isapplied. An emission wavelength of the light emitting elements 5 can bevisible, ultraviolet, or infrared light, or the like.

In the case where using the light emitting elements emit visible light,the emission color can be any of blue, green, and red light, forexample.

A white light emitting element such as a blue light emitting elementcoated with a fluorescent material can also be used.

The semiconductor materials used in the light emitting element 5 can beany compound semiconductor, such as group III-V, group II-VI, or thelike.

The light emitting elements 5 may be flip chip mounted or face-upmounted on the wiring member 13. As shown in FIGS. 3 and 4, in the caseof using flip chip mounting, the p-side electrode (i.e. anode) and then-side electrode (i.e. cathode) of each light emitting element 5 arebonded to a pair of wiring members 13 a and 13 b, respectively, via apair of conductive joining material. For the conductive joiningmaterial, an Sn—Ag—Cu-based, Sn—Cu-based, or Au—Sn-based solder, Aumetal bump, Ag paste, or the like, can be used.

In the case of using face-up mounting manner, each light emittingelement 5 may be bonded on the base body 11 and/or the wiring member 13by an insulating joining material, such as a resin, or any of theconductive joining materials mentioned above, and electrically connectedto the wiring pattern 13 by wires. In the case where the elementsubstrate of the light emitting element 5 is conductive, one of theelectrodes is electrically connected to the wiring member 13 a or 13 busing any of the aforementioned conductive joining materials, while theother electrode is electrically connected to another wiring member 13 aor 13 b using a wire.

Sealing Member

The sealing member 6, as shown in FIGS. 3 and 4, encloses and protectsthe light emitting element 5. The sealing member 6 is lighttransmissive. The sealing member 6 may be provided on the upper face ofthe flexible substrate 10 so as to cover the light emitting element 5.The viscosity of the material forms the sealing member 6 can be adjustedso as to be applicable by printing or by using a dispenser, for example.The sealing member 6 can be cured by way of heat treatment or UV lightirradiation. The sealing member 6 preferably has good adhesion with theflexible substrate 10 and the light emitting element 5. Also, thesealing member 6 preferably has flexibility. The emission wavelength andlight distribution characteristics of the light emitting device can beadjusted by containing wavelength conversion material such as aYAG-based, TAG-based, or silicate-based phosphor, or the like in thesealing, member 6. Also, an inorganic light diffusing material, such astitanium oxide, silicon oxide, alumina, zinc oxide, fine glass powder,or the like; or an organic light diffusing material, such as acrylic,polystyrene, or the like can be contained in the sealing member 6. Thesealing member 6 preferably has a convex shape from the perspective ofimproving light extraction efficiency as shown in FIG. 4. The shape ofthe sealing member 6 can be an approximate hemispherical shape, anoblong convex shape in a cross-sectional view, a circular or ellipticalshape in a plan view, for example.

Connector 3 and 4

The connectors 3 and 4 are disposed in correspondence to the positiveand negative polarities and disposed on the wiring pattern 13. Metalterminals such as DF59M manufactured by Hirose Electric Co., Ltd., ormolded metal terminals, such as DF61 manufactured by Hirose ElectricCo., Ltd., can be used as the connectors 3 and 4.

The p-side electrode of the light emitting element 5 is electricallyconnected to the connector 3 via the wiring member 13 a, and iselectrically connected to the positive terminal of an external powersupply via a wire harness, for example.

The n-side electrode of the light emitting element 5 is electricallyconnected to the connector 4 via the wiring member 13 b, and iselectrically connected to the negative terminal of an external powersupply via a wire harness, for example.

Examples of materials of the connectors 3 and 3 include rustproofedcopper with tinning plating. Examples of methods of joining theconnectors 3 and 4 with the wiring pattern 13 include reflow soldering,ultrasonic bonding, resistance welding, crimping, or the like.

Underlayer 7

The underlayer 7 is used as the base for the reflective layer 8. Asshown in FIGS. 3 and 4, an underlayer 7 is disposed on the flexiblesubstrate 10. The underlayer 7 preferably covers the wiring member 13and/or the base body 11 or the adhesive layer 12 partially or entirely,while exposing a portion of the wiring member 13. The underlayer 7 hasopenings (for example, a circular shape) for exposing a pair of wiringmembers 13 a and 13 b which correspond to a pair of positive andnegative polarities, and the groove between the pair of positive andnegative wiring members 13 a and 13 b. The size of the opening ispreferably formed in the minimum size required to enable the electricalconnection between the light emitting element 5 and the wiring pattern13 within the opening. The openings may have different in shape and sizeeach other, but are preferably the same in shape and size.

The underlayer 7 can include a thermosetting resin, thermoplastic resin,or the like, for example. Specific examples include modified epoxy resincompositions, such as epoxy resin compositions, silicone resincompositions, silicone modified epoxy resins, and the like; modifiedsilicone resin compositions, such as epoxy modified silicone resins, orthe like; polyimide resin compositions, modified polyimide resincompositions; polyphtalamide (PPA); polycarbonate resins; polyphenylenesulfide (PPS); liquid crystal polymers (LCP); ABS resins; phenol resins;acrylic resins; PBT resins, or the like.

The underlayer 7 preferably contains a material that reflects the lightemitted from the light emitting element 5, as well as the light whosewavelength has been converted by the wavelength conversion material. Thereflectance here with respect to the light described is preferably 60%or higher, more preferably 65% or higher, or 70% or higher. Examples ofsuch materials include light-reflecting materials. Examples oflight-reflecting materials include titanium dioxide, silicon dioxide,zirconium dioxide, potassium titanate, alumina, aluminum nitride,magnesium oxide, boron nitride, mullite, niobium oxide, and various rareearth oxides (for example, yttrium oxide and gadolinium oxide). Theunderlayer 7 may contain additives, including fibrous fillers, such asglass fibers and wollastonite, carbon, talc, and inorganic fillers suchas silicon oxide, or the like. The content of these materials can be ina range between 5 and 50 weight percent relative to the total weight ofthe underlayer 7.

The underlayer 7 is preferably formed in the thickness so that its upperface is lower than the upper face of the light emitting element 5. Theunderlayer 7 preferably has a thickness which does not undermine theflexibility of the flexible substrate 10, and can be formed, forexample, in thickness of about 1 to 50 μm. The underlayer 7 can beformed on one face of the base body by printing, potting, spin coating,dipping, or the like.

Reflective Layer 8

The reflective layer 8, as shown in FIGS. 3 and 4, is disposed on theupper face of the wiring pattern 13, particularly in the vicinity of thelight emitting section 2, that is the region corresponding to thethrough hole 21 or the opening of the reflective sheet 20, to increasethe light extraction efficiency of the light emitting device 1. In thisembodiment, the reflective layer 8 is formed in an annular shape in aplan view, disposed over the flexible substrate 10 spaced apart from thewiring pattern 13 in the stacking direction by the interposed underlayer7.

The reflective layer 8 is preferably disposed, for example, in the formof islands (that is, a plurality of separated reflective layers aredisposed) in correspondence with the quantity of the light emittingelements 5 disposed on the flexible substrates 10. The reflective layer8 is preferably formed as islands that are separated from one another.For example, The reflective layer 8 formed as islands may be separatedbased on the configuration of the light emitting section 2, or based onthe number of light emitting sections 2.

As shown in FIGS. 3 and 4, an edge of the reflective layer 8 on thelight emitting section 2 side (that is, an edge facing the opening) ispreferably more distant from the light emitting section 2 than the edgeof the underlayer 7 on the light emitting section 2 side. In this case,the distance between the edge of the reflective layer 8 closer to thelight emitting section 2 and the edge of the underlayer 7 closer to thelight emitting section 2 is from about 0.1 to 0.5 mm, for example. Anarea of the opening in the reflective layer 8 can be between about 0.8and 2.5 times, preferably between about 1 and 2 times, more preferablybetween about 1.3 and 1.6 times, of an area of the opening in theunderlayer 7.

The reflective layer 8 can be formed from any of the materials for theunderlayer 7 mentioned above. In other words, the reflective layer 8 canbe formed using, for example, a thermosetting resin, thermoplasticresin, or the like. Furthermore, it is preferable for these resins tocontain a light-reflecting material and/or other additives. Thereflective layer 8 preferably has the light reflectance of 80% or higherwith respect to the light from the light emitting element as well as thelight whose wavelength has been converted by wavelength conversionmaterial. It is preferable for the reflective layer 8 to have a higherlight reflectance than the underlayer 7. The reflective layer 8 cancontain the light-reflecting material and/or other additives in theratio of from 5 to 70 weight percent to the total weight of thereflective layer 8. The reflective layer 8, however, preferably containsthe same materials or have the same composition as the underlayer 7. Thelight reflectance of the reflective layer 8 mentioned above ispreferably higher than that of the underlayer 7. For this purpose, thereflective layer 8 preferably contains a light-reflecting materialhaving a higher light reflectance than that contained in the underlayer7 and/or contains a larger amount of the light-reflecting material.

By forming the reflective layer 8 on the underlayer 7, the role ofprotecting the wiring member 13 by ensuring the insulating properties ofthe flexible substrate 10 and the role of increasing the lightextraction efficiency by preventing the light emitted from the lightemitting elements 5 from being absorbed by the substrates can beseparated. More particularly, with this arrangement, even though theadhesion to the sealing member 6 and the light reflectance of the underlayer 7 and the reflective layer may be contrary properties, having theunderlayer 7 and the reflective layer 8 play different roles asdescribed above can attain a balance between the adhesion and lightreflectance properties.

The thickness of the reflective layer 8 can be suitably set within theranges discussed in connection to the thickness of the underlayer 7. Thethickness of the reflective layer 8 is preferably substantially the sameas that of the underlayer 7. The thickness of the reflective layer 8 ismore preferably set to achieve enough light reflectance in accordancewith the materials, particularly the type and the content of thelight-reflecting material, used to compose the reflective layer 8. Thereflective layer 8 can be formed separately from the underlayer 7 on oneface of the base body 11 by using any of the methods mentioned inconnection with the forming method for the underlayer 7.

Reflective Sheet 20

The reflective sheet 20 is provided to reflect the light from the lightemitting sections 2 to improve the effectiveness in extracting the lightfrom the light emitting device 1. The reflective sheet 20 is aninsulating sheet having light reflectance, and is preferably a flameretardant sheet. The reflective sheet 20 is preferably a film includinga synthetic resin, for example, a white polyethylene terephthalate(white PET) or a white glass fiber reinforced epoxy composite.

The size (that is, vertical and horizontal lengths in plan view), andthe thickness of the reflective sheet 20 are not particularly limited,as long as it has a large enough area for disposing the flexiblesubstrates 10 at a proper pitch required for the finished product of thelight emitting device 1 thereon. Its size can be suitably selected inaccordance with the purpose. For example, in the case where the lightemitting device is used for a television backlight application, thevertical and horizontal lengths may be several tens of centimeters orlarger. In this case, the thickness of the reflective sheet 20 may be ina range between about several tens and several hundreds of micrometers.Any commercially available PET film used as an LCD backlight reflectivesheet (for example, the white low specific gravity grade (E6SR) ofLumirror™, 188 m in thickness, high reflectance type (product number188) manufactured by Toray Industries, Inc., or the like) can beemployed as the reflective sheet 20.

Adhesive Member 30

The adhesive member 30 adheres the flexible substrates 10 and thereflective sheet 20 in the regions where the reflective layer 8 is notformed. The adhesive member 30 preferably has insulating properties, andfurthermore, preferably has high flame retardancy. A double-sided tape(pressure sensitive adhesive member) or the like can be preferably usedas the adhesive member 30. For example, an acrylic-based double-sidedtape manufactured by DIC Corporation (product number 8606TN), or thelike can be used. Also, a thermosetting or thermoplastic resin liquidadhesive, or a hot melt adhesive sheet can be also used for the adhesivemember 30.

Method for Producing a Light Emitting Device

Next, a method for producing the light emitting device 1 will beexplained.

First, as shown in FIG. 7A, a reflective sheet 20 is prepared. Thereflective sheet 20 is larger than the outer shape of the light emittingdevice 1. The reflective sheet 20 in this embodiment is horizontallyoblong, having a vertical length that is substantially equivalent to thefinished product height of the light emitting device 1.

Next, as shown in FIG. 7B, adhesive members 30 are disposed on the rearface 26 of the reflective sheet 20. In this embodiment, the adhesivemembers 30 have a length that is longer than the length of the flexiblesubstrates 10, and substantially the same width as that of the flexiblesubstrates 10. The adhesive members 30 in this embodiment areacrylic-based double-sided tape. A plurality of adhesive members 30 (sixshown here) are arranged at a certain pitch in the directionsubstantially perpendicular to the longitudinal direction of thereflective sheet 20, and disposed on the reflective sheet 20.

Next, as shown in FIG. 7C, through holes 21 and 22 are created in thereflective sheet 20, and the reflective sheet 20 is cut to a width ofthe finished product (the light emitting device 1). The through holes 21and 22 are preferably created simultaneously when the reflective sheet20 is cut to size. Here, the positions of the through holes 21 arematched to the positions of the light emitting sections 2 disposed onthe flexible substrates 10 which will be disposed. The positions of thethrough holes 22 are matched to the positions of the connectors 3 and 4of the flexible substrates 10. The through holes 21 and 22 are formed soas to penetrate through both the reflective sheet 20 and the adhesivemembers 30.

Then, as shown in FIG. 7D, the flexible substrates 10 are adhered to therear face 26 of the reflective sheet 20. The flexible substrates 10 arealigned so that the light emitting sections 2 disposed on the faces ofthe flexible substrates 10 opposite the back faces 16 are exposed at thethrough holes 21 of the reflective sheet 20. On the upper face 15 sideof the flexible substrates 10, the underlayer 7 at the peripheries ofthe light emitting sections 2 adheres to the reflective sheet 20 via theadhesive members 30. Also, the flexible substrates 10 are arranged sothat the connectors 3 and 4 disposed on each of flexible substrates 10are all aligned at one side. This can simplify the connection structurebetween an external power supply and the connectors 3 and 4.

The light emitting device 1 according to this embodiment includes aplurality of flexible substrates 10 lined up at a prescribed pitch andadhered to the reflective sheet 20 having a larger area than theflexible substrates. Thus, the insulating properties of the flexiblesubstrates 10 can be ensured by the reflective sheet 20. Moreover, thelight extraction efficiency of the light emitting device 1 can beincreased by disposing the reflective sheet 20 and reducing an amount ofthe light absorbed by the flexible substrates 10,

In the light emitting device 1, moreover, the reflective sheet 20integrated with the flexible substrates 10 can be deemed as a largedevice substrate. The light emitting device 1 having such a large areadevice substrate may not require the use of an insulating white ink,referred to as white resist above, in many regions of reflective sheet20 where no flexible substrates 10 are adhered, preferably the regionsaccounting for more than one half of the reflective sheet. Therefore,the amount of insulating white ink used in the light emitting device 1can be reduced. Accordingly, a bendable large area light emitting device1 can be produced inexpensively.

Furthermore, as shown in FIG. 4, the light emitting sections 2 includingthe light emitting elements 5 mounted on the flexible substrates 10 andcovered by the convex sealing member 6 may have light distributioncharacteristics of high light intensity over a wide angle region ascompared to, for example, a light emitting device having a package witha recess for light emitting elements disposed Accordingly, the lightemitting device 1 having a two-dimensional array of light emittingsections 2 lined up at certain intervals can be a surface emission lightsource having a wide light distribution angle, which can be a suitabledevice for a lighting device, such as a backlight.

Variation of Embodiment 1

As shown in FIG. 6, the light emitting device according to a variationof Embodiment 1 has a differently shaped wiring pattern 13 on theflexible substrate 10A from that of the light emitting device 1according to Embodiment 1. The flexible substrate 10A has wiring members13 a, 13 b, 13 c (collectively wiring member 13), which arranged alongthe longitudinal direction of the flexible substrate 10. Two lightemitting sections 2 are disposed between two of these three wiringmembers 13 a, 13 b, 13 c, respectively. The grooves between the wiringmembers 13 extend in the direction perpendicular to the longitudinaldirection of the flexible substrate 10A. The two adjacent light emittingsections 2 (light emitting elements 5) are disposed so that theseelectrodes having opposing polarities face to each other in thelongitudinal direction of the flexible substrates 10A and connected inseries.

As shown in FIG. 6, the width of the flexible substrate 10A is denotedas W2. The width of the wiring members 13 formed in one line in thelongitudinal direction of the flexible substrate 10A is denoted as L1,and the creepage distance is denoted as L2. In this case, preferably,the relationship expressed by the following formula (2) is established.The groove width between the wiring members 13 a and 13 b, and betweenthe wiring members 13 b and 13 c, is denoted as L3.

W2=L1+2×L2  formula (2)

Either the connector 3 or 4 in this variation may be placed at the leftend, and the other at the right end, of the flexible substrates 10A, asshown FIG. 14. At every groove between the wiring members 13, one pieceof light emitting element 5 may be electrically connected to a pair ofwiring members 13 interposing the groove (for example, a pair of thewiring members 13 a and 13 b, a pair of the wiring members 13 b and 13 cin FIG. 6).

According to this variation, the width W2 of the flexible substrate 10Acan be made narrower than the width W1 of the flexible substrate 10.This may reduce the amount of substrate material required and productioncosts.

Embodiment 2

When the light emitting device 1 is used as a direct-lit type backlightor a lighting device, for example, as shown in FIG. 8A, a light diffuserplate (light irradiation plate) 40, which is installed in front of thelight emitting device 1 at a prescribed distance may be used. FIG. 8Aschematically shows a cross section of the light emitting device 1according to Embodiment 1 cut at the positions of the light emittingsections 2 on the flexible substrates 10 when viewed from the side wherethe connectors 3 and 4 are located (the left hand side in FIG. 1).

As shown in FIG. 8A, a region 41 of the light diffuser plate 40substantially equidistant from two adjacent flexible substrates 10 maytend to have lower intensity of light from the light emitting sections 2of the light emitting device 1.

The light emitting device 1B according to Embodiment 2, as shown in FIG.8B, differs from the light emitting device 1 according to Embodiment 1by having a reflective sheet 20B that is three-dimensionally formed. Thereflective sheet 20B has through holes 21 as in the case of thereflective sheet 20, but is not flat overall, and has a plurality ofthree-dimensionally structured sections.

More specifically, the reflective sheet 20B has oblique face portions 27which extend obliquely so as to spread apart as they becomeperpendicularly (upwardly) more distant from the light emitting sections2 of the flexible substrates 10. The oblique face portions 27 shown inFIG. 8B are provided so as to interpose each through hole groupcomprising the through holes 21 linearly arranged in the longitudinaldirection of the flexible substrates 10 from both sides along thelongitudinal direction of the flexible substrates 10. The reflectivesheet 20B, moreover, has flat portions 27B between two oblique faceportions 27 provided in the spaces between two adjacent flexiblesubstrates 10.

The oblique face portions 27 can be formed by bending or vacuum formingthe flat reflective sheet 20. The oblique face portions 27 of thereflective sheet 20B provided between the flexible substrates 10 mayallow the light emitting device 1B to adjust the distribution of the LEDlight. In other words, the light transversely emitted from the lightemitting sections 2 mounted on the flexible substrates 10 can bedirected towards the regions 41 of the light diffuser plate 40 which maytend to have lower intensity of light, efficiently utilizing the lightemitted in a direction transverse to the optical axis.

Furthermore, the reflective sheet 20B having the oblique face portions27 will virtually have increased emission points, that is, portions ofthe oblique face portion 27 which reflect the light from the lightemitting sections 2 can be regarded as additional emission points,thereby allowing the light emitting device 1B to reduce the unevennessof illuminance at the light diffuser plate 40. This can reduce grainyappearance (granular appearance) caused by the so-called spots of light,which are the centers (forward direction) of the light emitting sections2 where the light intensity is high, occurring especially when the lightemitting device 1B is used in a thin direct-lit backlight or lightingdevice.

A size, angle, and location of the oblique face portions 27 describedabove can be suitably determined in accordance with the design of thelight emitting device 1. For example, assuming that the light intensityof the optical axis direction (0 degree direction) of the light emittingsection 2 is 100%, they are preferably set so as to result in lightintensity of at least 30% in an 80 degree direction measured from theoptical axis of the light emitting section 2.

The oblique face portions 27 described above can be any shape as long asthey can be used as a reflector to reflect the light transverselyemitted from the light emitting sections 2 upwardly. For example, asshown in FIG. 8C, they may be configured as in the case of the lightemitting device 1C according to a variation of Embodiment 2. In otherwords, in the light emitting device 1C, the oblique face portions 27 areprovided so as to interpose each through hole group consisting of thethrough holes 21 linearly arranged in the longitudinal direction of theflexible substrates 10 from both sides along the longitudinal directionof the flexible substrates 10, and two oblique face portions 27 locatedbetween two adjacent flexible substrates 10 are continuously formed. Thelight emitting device 1C, as in the case of the light emitting device1B, can efficiently utilize the light emitted in the directiontransverse to the optical axis, and reduce the unevenness of illuminanceat the light diffuser plate 40.

In the above-described light emitting devices 1B and 1C, the obliqueface portions 27 are disposed so as to reflect the light emitted from aplurality of light emitting sections 2 disposed in a row on each of theflexible substrates 10. Alternatively, the oblique face portions may bedisposed to reflect the light from individual light emitting sections 2.More specifically, the light emitting device may include a reflectivesheet having a ring-shaped oblique face portion provided so as tosurround at the periphery of each light emitting section 2. In otherwords, each oblique face portion may extend obliquely so as to spreadout from the rim of each through hole 21 of the reflective sheet 20 asit becomes perpendicularly more distant from the face of the flexiblesubstrate 10 on which the light emitting sections 2 are disposed.

Embodiment 3

As shown in FIG. 9, the light emitting device 1D according to Embodiment3 differs from the light emitting device 1 according to Embodiment 1 byhaving a reflective sheet 20D that having a circular shape in plan view.In the light emitting device 1D, a plurality of flexible substrates 10(five shown here—10 a, 10 b, 10 c, 10 d, and 10 e) are adhered to therear face 26 of the reflective sheet 20D in a stripe pattern at a pitch.The flexible substrate 10 c located in the center of the reflectivesheet 20D is set to the largest length, the flexible substrates 10 a and10 e located near the edge are set to the smallest length, and theflexible substrates 10 b and 10 d positioned in between are set to themiddle length.

The light emitting device 1D can be produced in similar process to inthe case of the light emitting device 1, such as creating through holes21 and 22 in an unprocessed reflective sheet 20 in alignment with thepositions of the light emitting sections 2 and connectors 3 and 4,respectively, of the flexible substrates 10, and achieving thereflective sheet 20D by cutting in accordance with the finished productshape of the light emitting device 1D (that is, a circular shape).

Embodiment 4

Another embodiment having a different reflective sheet shape will beexplained next.

As shown in FIG. 10, the light emitting device 1E according toEmbodiment 4 differs from the light emitting device 1 according toEmbodiment 1 by having a narrow line shape reflective sheet 20E. In thelight emitting device 1E, a plurality of flexible substrates 10 (fourshown here) are arranged linearly along the longitudinal direction ofthe flexible substrates 10 at a prescribed pitch, and adhered to therear face 26 of the reflective sheet 20E.

The light emitting device 1E can be produced in similar process to inthe case of the light emitting device 1, such as creating through holes21 and 22 in an unprocessed reflective sheet 20 in alignment with thepositions of the light emitting sections 2 and connectors 3 and 4,respectively, of the flexible substrates 10, and achieving thereflective sheet 20E by cutting in accordance with the finished productshape of the light emitting device 1E.

Embodiment 5

In the case where the light emitting device 1 according to Embodiment 1is used in a backlight for a television, for example, the vertical andhorizontal lengths of the light emitting device 1, i.e., the verticaland horizontal lengths of the reflective sheet 20, may be at leastseveral tens of centimeters, exceeding one meter in some cases. Apackaging cost required for the light emitting device 1 tends to easilyincrease as the area of the light emitting device 1, or the reflectivesheet 20, increases. For reducing the packaging cost, the light emittingdevice 1F according to Embodiment 5, as shown in FIGS. 11A and 11B,differs from the light emitting device 1 according to Embodiment 1 byhaving a reflective sheet 20F which is provided with ancillary sections28 for packaging purposes.

The ancillary sections 28 are provided at the periphery of the part thatactually functions as the light emitting device 1. For this purpose, thereflective sheet 20F is formed in a slightly larger size than that ofthe reflective sheet 20 of the light emitting device 1 according toEmbodiment 1. The reflective sheet 20F includes the reflective sheet 20of the light emitting device 1 in the center, and has the ancillarysections 28 at the four sides of the rectangle reflective sheet 20provided along cutting guide lines 28L by providing cut off lines likebroken-line in the reflective sheet 20F for separating the reflectivesheet 20 and the ancillary section 28 later. Here, the ancillarysections 28 are configured as four roughly narrow rectangular partsalong the cutoff lines 28L, and through holes 29 are created at fourcorners.

The process for producing the light emitting device 1F differs from thatfor the light emitting device 1 such that a reflective sheet larger thanthe outer shape of the light emitting device 1 is prepared, which is cutto size after providing cutting guide lines 28L along the outer edge ofthe light emitting device 1 while reserving the ancillary sections 28.Also, the process for producing the light emitting device 1F includingcreating through holes 21 and 22 in alignment with the positions of thelight emitting sections 2 and the connectors 3 and 4, respectively, ofthe flexible substrates 10, and achieving the reflective sheet 20F bycutting in accordance with the finished product shape of the lightemitting device 1F including the ancillary sections 28. The lightemitting device 1F can otherwise be produced in similar manner to in thecase of the light emitting device 1. The through holes 29 in theancillary sections 28 at four corners of the reflective sheet 20 may beformed as needed. The through holes 29 can be created at the same timethe through holes 21 and 22 are created.

In packaging the light emitting devices 1F, as shown in FIG. 11C, theproducts (light emitting devices 1F) are stacked, and, for example,stapled together at several locations in the ancillary sections 28 sothat the light emitting devices 1F may not shift. In the cases wherethrough holes 29 are provided in the ancillary sections 28, the lightemitting devices 1F can be bundled using strings fed through the holes29 so they may not shift. These light emitting devices 1F may be thenplaced in a corrugated cardboard box, for example. An insulating filmmay be laid over the outermost surface of the stacked products.

Since the products (light emitting devices 1F) are held together usingthe ancillary sections 28, shifting during transportation can bereduced, which can reduce the occurrences of scratches attributable toshifting of the products.

Following the transportation, the light emitting devices 1F may beunpacked, removed the ancillary sections 28 along the cutting guidelines 28L of the products (light emitting devices 1F), and used as theregular light emitting devices 1 by users. In the case where lightemitting devices are packed in a corrugated cardboard box, breaking orchipping at the edges of the light emitting devices may occur. In thecase of the light emitting device 1F, however, the ancillary sections 28which are the edges of the products and tend to be damaged can beremoved.

As explained above, according to the light emitting device 1F, evenusing simple packaging way such as stacking and placing the products(light emitting devices 1F) in a corrugated cardboard box, (1) breakingand chipping of the edges of the product can be reduced by removing theancillary sections 28, and (2) the occurrences of scratches can bereduced by reducing the products from shifting during transportation.

By simplifying the packaging, the cost required for packaging can bereduced even for a large area light emitting device 1 therefore theprice of the light emitting device can be reduced.

Embodiment 6

As shown in FIG. 12, the light emitting device 1G according toEmbodiment 6 differs from the light emitting device 1 according toEmbodiment 1 such that the flexible substrates 10 are laminated with thereflective sheet 20 disposed on the upper face 15 side and theinsulating sheet 50 disposed on the back face 16 side. The insulatingsheet 50 is continuously adhered to the faces of the flexible substrates10 opposite the upper faces 15 where the light emitting sections 2 aredisposed (i.e., the back faces 16), and the same face of the reflectivesheet 20 (the rear face 26) as that adhering to the flexible substrates10.

The insulating sheet 50 is preferably made of a synthetic resin, such aspolyethylene terephthalate (PET), or the like, a metal sheet withinsulating coating, or a metal sheet laminated with a synthetic resinfilm, such as PET. The insulating sheet 50 is formed larger than theflexible substrates 10, and when using a single insulating sheet 50, itpreferably has substantially the same size as that of the reflectivesheet 20. The thickness of the insulating sheet 50 can be the samethickness as that of the reflective sheet 20 in the case of the materialof insulating sheet 50 is synthetic resin like PET. A plurality ofinsulating sheets that are smaller in size than the reflective sheet 20can be used in the light emitting device 1G instead of one insulatingsheet 50.

The light emitting device 1G can be produced by further performing astep of providing the insulating sheet 50 following the production ofthe light emitting device 1. More specifically, as shown in FIG. 7D, thelight emitting device 1 where the flexible substrates 10 are adhered onthe rear face 26 of the reflective sheet 20 is prepared in advance. Anadhesive member 30G, such as a double-sided tape, is provided on oneface of the insulating sheet 50 in advance. By adhered that face of theinsulating sheet 50 to the rear face 26 of the reflective sheet 20 withthe adhesive member 30G, the light emitting device 1G can be produced.Alternatively, the adhesive member 30G may be provided on the rear face26 of the reflective sheet 20 first, followed by bonding the insulatingsheet 50 to the adhesive member 30G. A size, shape, and the quantity ofthe adhesive member 30G may be suitably set. According to the lightemitting device 1G, the strength can be increased.

Variation of Embodiment 6

The creepage distance as shown in FIGS. 5 and 6 is normally required inorder to ensure the insulating properties of the flexible substrate 10and 10 a. In the case where the creepage distances is eliminated bymaking an edge of the wiring pattern 13 and an edge of the base body 11of the flexible substrates 10 or 10A substantially identical in a planview, a side face of the wiring member 13 will be bare on the edge ofthe flexible substrate 10 or 10A, which may raise a concern caused bystatic electricity when handling the flexible substrates 10. In thelight emitting device 1G according to Embodiment 6, however, theflexible substrates 10 are laminated with the reflective sheet 20 andthe insulating sheet 50, and thus the side faces of the wiring member 13on the flexible substrates 10 will not be bare. Thus, the flexiblesubstrates 10 can be protected against static electricity during thehandling of the light emitting device 1 with the flexible substrates 10,and insulating properties in the creepage direction can be ensured atlow cost by pasting the insulating sheet 50 to the back faces 16 of theflexible substrates 10.

In a variation of Embodiment 6, as shown in FIG. 13, the flexiblesubstrate 10G has no creepage distances. As shown in FIG. 13, the widthof the flexible substrate 10G is denoted as W3. The width of the wiringpattern 13 formed along a line in the longitudinal direction of theflexible substrate 10G is denoted as L1, and the creepage distance is 0.In this case, the relationship expressed by the following formula (3) isestablished. The groove width between the wiring members 13 a, 13 b, 13c is denoted as L3.

W3=L1  formula (3)

The flexible substrate 10G shown in FIG. 13 can be produced by preparinga flexible substrate collective sheet 60 shown in FIG. 14, followed byseparating them, for example. The collective sheet 60 shown herecorresponds to ten flexible substrates. On each substrate, the connector3 is disposed at the left end, and the connector 4 is disposed at theright end. In the collective sheet 60, the width of each of these tenflexible substrates, which will be used as the flexible substrates 10Glater is preset to the width W3 shown in FIG. 13, i.e., the width L1 ofthe wiring pattern 13, unlike the flexible substrates 10A.

By producing a collective sheet 60 designed as above, the width W3 ofthe flexible substrates 10G described above can be reduced, for example,to a 60% value of the width W2 of the flexible substrate 10A shown inFIG. 6. The elimination of the creepage distances in this way can reducethe areas of flexible substrates 10G, and thus can reduce the productioncosts of the flexible substrates 10G.

Embodiment 7

As shown in FIGS. 15 and 16, the light emitting device 1H according toEmbodiment 7 differs from the light emitting device 1 according toEmbodiment 1 such that it is a double-side emitting type light emittingdevice where light can be emitted from the rear face side. The lightemitting device 1H can produced by adhering the flexible substrates 10to the flexible substrates 10H via the adhesive member 30. The lightemitting device 1H can emit the light from the light emitting sections 2to both the front and rear faces side of the light emitting device 1H.The flexible substrates 10H here have similar configuration as that ofthe flexible substrates 10.

The light emitting device 1H can be produced by further performing astep of bonding the flexible substrates 10H after producing a lightemitting device 1. For example, the light emitting device 1 in which theflexible substrates 10 are bonded on the rear face 26 of the reflectivesheet 20, as shown in FIG. 7D, is prepared in advance. A collectivesheet of the flexible substrates 10H is prepared in advance, and theadhesive member 30, such as a double-sided tape, for example, isprovided on the rear face of the collective sheet. The light emittingdevice 1H can be produced by bonding the back faces of the flexiblesubstrates 10H, which have been separated from the collective sheet, tothe back faces 16 of the flexible substrates 10 on the reflective sheet20. Alternatively, the adhesive member 30 may be first provided on theback faces 16 of the flexible substrates 10 on the reflective sheet 20,followed by bonding the flexible substrates 10H to the adhesive member30.

According to the light emitting device 1H, a flexible double-sidedemission type light emitting device can be produced at low cost. Thelight emitting device 1H, being a double-sided emission type, can beapplied to, for example, a double-sided internally illuminated signboardwhere both the front and rear faces are signboard faces illuminated by alight emitting device installed inside.

Embodiment 8

The light emitting devices according to the embodiments preferablyfurther include a feature to reduce warping that can be caused by, forexample, temperature and/or humidity. As shown in FIG. 17, the lightemitting device 1K according to Embodiment 8 differs from the lightemitting device 1 according to Embodiment 1 by having a reflective sheet20K provided with broken-line shaped slits 70. The slits 70 are providedto reduce warping resulting from, for example, temperature and/orhumidity. The slits 70 are created in the direction substantiallyperpendicular to the upper face of the flexible substrates 10 byperforating. A plurality of slits 70 are created at positions thatdeviate from the light emitting sections 2 of the flexible substrates10.

As for the slits, the distance between them, and the length and widthof, the holes (that is, slits 70) can be suitably selected depending onthe strength required of the light emitting device 1K and within theranges that can ensure the insulating properties of the flexiblesubstrates 10, for example. The slits are preferably provided next tothe light emitting sections 2 of the flexible substrates 10. The slitsmay be formed at mid position between two adjacent light emittingsections 2 located on flexible substrates 10, or a position that deviatefrom mid position. Moreover, multiple slits may be created between twoadjacent light emitting sections 2 of the flexible substrates 10. Thenumber of slits is can be suitably selected. The sizes of the slits 70may be common to all or different. The spacing between the slits may becommon to all or different.

In producing the light emitting device 1K, a step of perforating theunprocessed reflective sheet 20 is additionally performed prior todisposing the adhesive member 30 on the reflective sheet 20. Morespecifically, in the case where the reflective sheet 20 is prepared asshown in FIG. 7A, multiple slits are vertically formed while avoidingthe positions of the light emitting sections 2 on the flexiblesubstrates 10. Thereafter, the device can be produced in the same manneras in the case of the light emitting device 1.

In the case where the respective materials mentioned earlier are usedfor the reflective sheet 20K and the flexible substrates 10 of the lightemitting device 1K, the reflective sheet 20K will have a higher rate ofheat shrinkage than the flexible substrates 10. For example, underconstant temperature and constant humidity conditions, a member whichthe two materials having different rates of heat shrinkage andcoefficients of thermal expansion are bonded tends to reveal differentdimensional changes between the two bonded materials, which may causewarping of the member. However, the light emitting device 1K employs thereflective sheet 20K provided with the slits 70, and thus warping can bereduced as the gaps formed by the slits 70 expand when the reflectivesheet 20K shrinks due to temperature and/or humidity. According to thelight emitting device 1K, therefore, warping can be effectively reducedeven when the device is placed, for example, in a high-temperature andhigh-humidity location, or is heated or dried.

Other Variations

In each of the embodiments discussed above, the reflective layer 8formed on the flexible substrates 10 are disposed spaced apart from thewiring pattern in the stacking direction by interposing the underlayer7. However, the underlayer 7 may not be disposed immediately below thereflective layer 8, and the reflective layer 8 may be disposed directlyon the wiring pattern.

Furthermore, the underlayer 7 may not be used, as each of the lightemitting devices according to the above embodiments can ensure theinsulating properties of the flexible substrates 10 using the reflectivesheet 20. In this case, the production costs of a large area lightemitting device can be further reduced.

In the light emitting devices according to the embodiments discussedabove, the connectors 3 and 4 on the flexible substrates 10 areconnected to an external power supply using a wire harness. However, arelay board provided with a wiring pattern can be directly connected tothe wiring member 13 by soldering, without using the connectors 3 and 4.The relay board may be a general circuit board, but is preferably anoblong flexible substrate. Such a construction requires no wireharnesses or connectors, and thus can reduce materials costs. Thisincreases the cost reduction effect particularly in the case where alarge number of flexible substrates are used.

INDUSTRIAL APPLICABILITY

The light emitting devices according to the embodiments described inthis disclosure can be used as various types of light sources applicableto lighting fixtures, various indicators, automotive lights, displays,liquid crystal display backlights, sensors, traffic signals, automotiveparts, signboard channel letters, and the like.

What is claimed is:
 1. A light emitting device comprising: a pluralityof oblong flexible substrates, each flexible substrate comprising asheet-shaped base body and a wiring pattern formed on one face of thebase body, and each flexible substrate having a plurality of lightemitting sections disposed thereon; a plurality of a reflective layers,each reflective layer being disposed at a periphery of a respectivelight emitting section above a respective flexible substrate; aninsulating reflective sheet made of a light reflecting resin, thereflective sheet having a plurality of through holes located such thatthe light emitting sections and at least a portion of the reflectivelayers are exposed via the through holes; and a plurality of adhesivemembers, each adhesive member adhering a respective flexible substrateto the reflective sheet in regions where the reflective layer is notformed.
 2. The light emitting device according to claim 1, furthercomprising an underlayer disposed on a portion of each of the flexiblesubstrates, wherein at least a portion of each underlayer is interposedbetween each flexible substrate and each respective reflective layer. 3.The light emitting device according to claim 2, wherein each of theflexible substrates includes a region where the base body and the wiringpattern are stacked in that order, and wherein at least one of theflexible substrates includes, in an area above the wiring pattern, aregion where the underlayer and the reflective layer are stacked on thewiring pattern, and a second region where the underlayer is stacked onthe wiring pattern but exposed from the reflective layer.
 4. The lightemitting device according to claim 1, wherein the flexible substratesare lined up in a direction substantially perpendicular to alongitudinal direction of the flexible substrates.
 5. The light emittingdevice according to claim 1, wherein the flexible substrates arelinearly arranged along a longitudinal direction of the flexiblesubstrates.
 6. The light emitting device according to claim 1, whereinthe reflective sheet has oblique face portions extending obliquely fromportions of the reflective sheet that are adhered to the flexiblesubstrates so as to spread apart from one another as they become moredistant from the light emitting sections of the flexible substrates, theoblique face portions being disposed so as to interpose and extend alonggroups of through holes that are linearly arranged in longitudinaldirections of the flexible substrates.
 7. The light emitting deviceaccording to claim 1, wherein the reflective sheet has an oblique faceportion for each of the through holes extending obliquely from a portionof the reflective sheet that is adhered to each flexible substrate so asto spread apart from the rim of the through hole as it becomes moredistant from the light emitting sections of the flexible substrates. 8.The light emitting device according to claim 1, wherein the lightemitting sections have a plurality of light emitting elements that areelectrically connected to the wiring pattern via electrodes of the lightemitting elements, the flexible substrates have a single row of wiringmembers extending between at least two adjacent light emitting elements,and the at least two adjacent light emitting elements are disposed andconnected in series so that electrodes of opposing polarities face oneanother.
 9. The light emitting device according to claim 1, furthercomprising an insulating sheet continuously adhered to the faces of theflexible substrates opposite the faces on which the light emittingsections are disposed, and to the same face of the reflective sheet asthat adhered to the flexible substrates.
 10. The light emitting deviceaccording to claim 1, wherein (i) faces of the flexible substratesbonded to the reflective sheet that are opposite faces on which lightemitting sections of the flexible substrates are disposed, are adheredto (ii) faces of a plurality of other flexible substrates opposite faceson which light emitting sections of the other flexible substrates aredisposed.
 11. The light emitting device according to claim 1, whereinthe reflective sheet has slits extending in a direction substantiallyperpendicular to a longitudinal direction of the flexible substrates, aplurality of the slits being located at positions that deviate from thelight emitting sections of the flexible substrates.